How to recursively sort YAML using CommentedMap?

问题

There's a good example of sorting at the top level, but how would you recurse the sort at all levels?

This seems to work:

   def sort_commentedmap(self, od):
       res = ruamel.yaml.comments.CommentedMap()
       for k in sorted(od):
           res[k] = od[k]
           if not isinstance(od[k], ruamel.yaml.comments.CommentedSeq):
               continue
           for idx, i in enumerate(od[k]):
               if isinstance(i, str):
                   res[k][int(idx)] = i
               else:
                   res[k][int(idx)] = self.sort_commentedmap(i)
       return res

Does this look correct?

回答1:

In YAML you can have sequences nested in mappings and mappings nested in sequences. You can also have scalar nodes, but those cannot nest anything.

So you need a function that processes the three elements, doing nothing on scalars. It should recursively access the elements of a sequence in case a mapping is nested under one of its elements. And when you have a mapping, both recurse into the values (which might have some other mapping down below), and sort the mapping itself by key.

In the following I use .insert which preserves end-of-line comments, something that would be more difficult if you created a new CommentedMap. That this works is because .pop() doesn't delete an end-of-line comment associated with a key, and reinstering the key will get the comment re-associated.

Running:

import sys
import ruamel.yaml

yaml_str = """\
f: 3
e: 
- 10     # sequences can have nodes that are mappings
- 11
- x: A
  y: 30
  z: 
    m: 51  # this should be last
    l: 50
    k: 49  # this should be first 
d: 1
"""

def recursive_sort_mappings(s):
    if isinstance(s, list):
        for elem in s:
            recursive_sort_mappings(elem)
        return 
    if not isinstance(s, dict):
        return
    for key in sorted(s, reverse=True):
        value = s.pop(key)
        recursive_sort_mappings(value)
        s.insert(0, key, value)


yaml = ruamel.yaml.YAML()
data = yaml.load(yaml_str)
recursive_sort_mappings(data)
yaml.dump(data, sys.stdout)

gives:

d: 1
e:
- 10     # sequences can have nodes that are mappings
- 11
- x: A
  y: 30
  z:
    k: 49  # this should be first 
    l: 50
    m: 51  # this should be last
f: 3

(Python 2.7/3.4/3.5/3.6/3.7, ruamel.yaml 0.15.44)

来源：https://stackoverflow.com/questions/51386822/how-to-recursively-sort-yaml-using-commentedmap

标签

python

python-3.x

YAML

ruamel.yaml